Incorporating availability for detection in estimates of bird abundance

Duane R Diefenbach, Matt Richard Marshall, Jennifer A. Mattice, Daniel W. Brauning

Research output: Contribution to journalArticle

72 Citations (Scopus)

Abstract

Several bird-survey methods have been proposed that provide an estimated detection probability so that bird-count statistics can be used to estimate bird abundance. However, some of these estimators adjust counts of birds observed by the probability that a bird is detected and assume that all birds are available to be detected at the time of the survey. We marked male Henslow's Sparrows (Ammodramus henslowii) and Grasshopper Sparrows (A. savannarum) and monitored their behavior during May-July 2002 and 2003 to estimate the proportion of time they were available for detection. We found that the availability of Henslow's Sparrows declined in late June to <10% for 5- or 10-min point counts when a male had to sing and be visible to the observer; but during 20 May-19 June, males were available for detection 39.1% (SD = 27.3) of the time for 5-min point counts and 43.9% (SD = 28.9) of the time for 10-min point counts (n = 54). We detected no temporal changes in availability for Grasshopper Sparrows, but estimated availability to be much lower for 5-min point counts (10.3%, SD = 12.2) than for 10-min point counts (19.2%, SD = 22.3) when males had to be visible and sing during the sampling period (n = 80). For distance sampling, we estimated the availability of Henslow's Sparrows to be 44.2% (SD = 29.0) and the availability of Grasshopper Sparrows to be 20.6% (SD = 23.5). We show how our estimates of availability can be incorporated in the abundance and variance estimators for distance sampling and modify the abundance and variance estimators for the double-observer method. Methods that directly estimate availability from bird counts but also incorporate detection probabilities need further development and will be important for obtaining unbiased estimates of abundance for these species.

Original languageEnglish (US)
Pages (from-to)96-106
Number of pages11
JournalAuk
Volume124
Issue number1
DOIs
StatePublished - Jan 1 2007

Fingerprint

bird
birds
Passeriformes
grasshopper
sampling
survey method
detection
statistics
methodology
Ammodramus savannarum
method

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

Cite this

Diefenbach, D. R., Marshall, M. R., Mattice, J. A., & Brauning, D. W. (2007). Incorporating availability for detection in estimates of bird abundance. Auk, 124(1), 96-106. https://doi.org/10.1642/0004-8038(2007)124[96:IAFDIE]2.0.CO;2
Diefenbach, Duane R ; Marshall, Matt Richard ; Mattice, Jennifer A. ; Brauning, Daniel W. / Incorporating availability for detection in estimates of bird abundance. In: Auk. 2007 ; Vol. 124, No. 1. pp. 96-106.
@article{28518b5edddf40b088be628a9dff9c01,
title = "Incorporating availability for detection in estimates of bird abundance",
abstract = "Several bird-survey methods have been proposed that provide an estimated detection probability so that bird-count statistics can be used to estimate bird abundance. However, some of these estimators adjust counts of birds observed by the probability that a bird is detected and assume that all birds are available to be detected at the time of the survey. We marked male Henslow's Sparrows (Ammodramus henslowii) and Grasshopper Sparrows (A. savannarum) and monitored their behavior during May-July 2002 and 2003 to estimate the proportion of time they were available for detection. We found that the availability of Henslow's Sparrows declined in late June to <10{\%} for 5- or 10-min point counts when a male had to sing and be visible to the observer; but during 20 May-19 June, males were available for detection 39.1{\%} (SD = 27.3) of the time for 5-min point counts and 43.9{\%} (SD = 28.9) of the time for 10-min point counts (n = 54). We detected no temporal changes in availability for Grasshopper Sparrows, but estimated availability to be much lower for 5-min point counts (10.3{\%}, SD = 12.2) than for 10-min point counts (19.2{\%}, SD = 22.3) when males had to be visible and sing during the sampling period (n = 80). For distance sampling, we estimated the availability of Henslow's Sparrows to be 44.2{\%} (SD = 29.0) and the availability of Grasshopper Sparrows to be 20.6{\%} (SD = 23.5). We show how our estimates of availability can be incorporated in the abundance and variance estimators for distance sampling and modify the abundance and variance estimators for the double-observer method. Methods that directly estimate availability from bird counts but also incorporate detection probabilities need further development and will be important for obtaining unbiased estimates of abundance for these species.",
author = "Diefenbach, {Duane R} and Marshall, {Matt Richard} and Mattice, {Jennifer A.} and Brauning, {Daniel W.}",
year = "2007",
month = "1",
day = "1",
doi = "10.1642/0004-8038(2007)124[96:IAFDIE]2.0.CO;2",
language = "English (US)",
volume = "124",
pages = "96--106",
journal = "Auk",
issn = "0004-8038",
publisher = "Ornithological Societies of North America",
number = "1",

}

Diefenbach, DR, Marshall, MR, Mattice, JA & Brauning, DW 2007, 'Incorporating availability for detection in estimates of bird abundance', Auk, vol. 124, no. 1, pp. 96-106. https://doi.org/10.1642/0004-8038(2007)124[96:IAFDIE]2.0.CO;2

Incorporating availability for detection in estimates of bird abundance. / Diefenbach, Duane R; Marshall, Matt Richard; Mattice, Jennifer A.; Brauning, Daniel W.

In: Auk, Vol. 124, No. 1, 01.01.2007, p. 96-106.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Incorporating availability for detection in estimates of bird abundance

AU - Diefenbach, Duane R

AU - Marshall, Matt Richard

AU - Mattice, Jennifer A.

AU - Brauning, Daniel W.

PY - 2007/1/1

Y1 - 2007/1/1

N2 - Several bird-survey methods have been proposed that provide an estimated detection probability so that bird-count statistics can be used to estimate bird abundance. However, some of these estimators adjust counts of birds observed by the probability that a bird is detected and assume that all birds are available to be detected at the time of the survey. We marked male Henslow's Sparrows (Ammodramus henslowii) and Grasshopper Sparrows (A. savannarum) and monitored their behavior during May-July 2002 and 2003 to estimate the proportion of time they were available for detection. We found that the availability of Henslow's Sparrows declined in late June to <10% for 5- or 10-min point counts when a male had to sing and be visible to the observer; but during 20 May-19 June, males were available for detection 39.1% (SD = 27.3) of the time for 5-min point counts and 43.9% (SD = 28.9) of the time for 10-min point counts (n = 54). We detected no temporal changes in availability for Grasshopper Sparrows, but estimated availability to be much lower for 5-min point counts (10.3%, SD = 12.2) than for 10-min point counts (19.2%, SD = 22.3) when males had to be visible and sing during the sampling period (n = 80). For distance sampling, we estimated the availability of Henslow's Sparrows to be 44.2% (SD = 29.0) and the availability of Grasshopper Sparrows to be 20.6% (SD = 23.5). We show how our estimates of availability can be incorporated in the abundance and variance estimators for distance sampling and modify the abundance and variance estimators for the double-observer method. Methods that directly estimate availability from bird counts but also incorporate detection probabilities need further development and will be important for obtaining unbiased estimates of abundance for these species.

AB - Several bird-survey methods have been proposed that provide an estimated detection probability so that bird-count statistics can be used to estimate bird abundance. However, some of these estimators adjust counts of birds observed by the probability that a bird is detected and assume that all birds are available to be detected at the time of the survey. We marked male Henslow's Sparrows (Ammodramus henslowii) and Grasshopper Sparrows (A. savannarum) and monitored their behavior during May-July 2002 and 2003 to estimate the proportion of time they were available for detection. We found that the availability of Henslow's Sparrows declined in late June to <10% for 5- or 10-min point counts when a male had to sing and be visible to the observer; but during 20 May-19 June, males were available for detection 39.1% (SD = 27.3) of the time for 5-min point counts and 43.9% (SD = 28.9) of the time for 10-min point counts (n = 54). We detected no temporal changes in availability for Grasshopper Sparrows, but estimated availability to be much lower for 5-min point counts (10.3%, SD = 12.2) than for 10-min point counts (19.2%, SD = 22.3) when males had to be visible and sing during the sampling period (n = 80). For distance sampling, we estimated the availability of Henslow's Sparrows to be 44.2% (SD = 29.0) and the availability of Grasshopper Sparrows to be 20.6% (SD = 23.5). We show how our estimates of availability can be incorporated in the abundance and variance estimators for distance sampling and modify the abundance and variance estimators for the double-observer method. Methods that directly estimate availability from bird counts but also incorporate detection probabilities need further development and will be important for obtaining unbiased estimates of abundance for these species.

UR - http://www.scopus.com/inward/record.url?scp=33846834016&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33846834016&partnerID=8YFLogxK

U2 - 10.1642/0004-8038(2007)124[96:IAFDIE]2.0.CO;2

DO - 10.1642/0004-8038(2007)124[96:IAFDIE]2.0.CO;2

M3 - Article

AN - SCOPUS:33846834016

VL - 124

SP - 96

EP - 106

JO - Auk

JF - Auk

SN - 0004-8038

IS - 1

ER -